[FFmpeg-devel] [PATCH] avcodec/vp9_superframe_split_bsf: Check in size

[FFmpeg-devel] [PATCH] avcodec/vp9_superframe_split_bsf: Check in size

[Michael Niedermayer]

Fixes: Out of array read
Fixes: 45137/clusterfuzz-testcase-minimized-ffmpeg_BSF_VP9_SUPERFRAME_SPLIT_fuzzer-4984270639202304

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavcodec/vp9_superframe_split_bsf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/vp9_superframe_split_bsf.c b/libavcodec/vp9_superframe_split_bsf.c
index ed0444561a..481484a4f0 100644
--- a/libavcodec/vp9_superframe_split_bsf.c
+++ b/libavcodec/vp9_superframe_split_bsf.c
@@ -51,7 +51,7 @@ static int vp9_superframe_split_filter(AVBSFContext *ctx, AVPacket *out)
             return ret;
         in = s->buffer_pkt;
 
-        marker = in->data[in->size - 1];
+        marker = in->size ? in->data[in->size - 1] : 0;
         if ((marker & 0xe0) == 0xc0) {
             int length_size = 1 + ((marker >> 3) & 0x3);
             int   nb_frames = 1 + (marker & 0x7);
-- 
2.17.1

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Re: [FFmpeg-devel] [PATCH] avcodec/vp9_superframe_split_bsf: Check in size

[Andreas Rheinhardt]

Michael Niedermayer:
> Fixes: Out of array read
> Fixes: 45137/clusterfuzz-testcase-minimized-ffmpeg_BSF_VP9_SUPERFRAME_SPLIT_fuzzer-4984270639202304
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavcodec/vp9_superframe_split_bsf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavcodec/vp9_superframe_split_bsf.c b/libavcodec/vp9_superframe_split_bsf.c
> index ed0444561a..481484a4f0 100644
> --- a/libavcodec/vp9_superframe_split_bsf.c
> +++ b/libavcodec/vp9_superframe_split_bsf.c
> @@ -51,7 +51,7 @@ static int vp9_superframe_split_filter(AVBSFContext *ctx, AVPacket *out)
>              return ret;
>          in = s->buffer_pkt;
>  
> -        marker = in->data[in->size - 1];
> +        marker = in->size ? in->data[in->size - 1] : 0;
>          if ((marker & 0xe0) == 0xc0) {
>              int length_size = 1 + ((marker >> 3) & 0x3);
>              int   nb_frames = 1 + (marker & 0x7);

There is a second place in this BSF where data might be read in the
absence of data, namely if one of the frames in a superframe have size
of zero (its attempted to read its profile; no actual read takes place
due to the checks of the get_bits API, but it is nevertheless invalid
data). See
https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200530160541.29517-7-andreas.rheinhardt@gmail.com/;
also see
https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200530160541.29517-11-andreas.rheinhardt@gmail.com/
and
https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200530160541.29517-1-andreas.rheinhardt@gmail.com/

- Andreas
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Re: [FFmpeg-devel] [PATCH] avcodec/vp9_superframe_split_bsf: Check in size

[Michael Niedermayer]

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On Fri, Mar 18, 2022 at 06:56:19PM +0100, Andreas Rheinhardt wrote:
> Michael Niedermayer:
> > Fixes: Out of array read
> > Fixes: 45137/clusterfuzz-testcase-minimized-ffmpeg_BSF_VP9_SUPERFRAME_SPLIT_fuzzer-4984270639202304
> > 
> > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > ---
> >  libavcodec/vp9_superframe_split_bsf.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/libavcodec/vp9_superframe_split_bsf.c b/libavcodec/vp9_superframe_split_bsf.c
> > index ed0444561a..481484a4f0 100644
> > --- a/libavcodec/vp9_superframe_split_bsf.c
> > +++ b/libavcodec/vp9_superframe_split_bsf.c
> > @@ -51,7 +51,7 @@ static int vp9_superframe_split_filter(AVBSFContext *ctx, AVPacket *out)
> >              return ret;
> >          in = s->buffer_pkt;
> >  
> > -        marker = in->data[in->size - 1];
> > +        marker = in->size ? in->data[in->size - 1] : 0;
> >          if ((marker & 0xe0) == 0xc0) {
> >              int length_size = 1 + ((marker >> 3) & 0x3);
> >              int   nb_frames = 1 + (marker & 0x7);
> 
> There is a second place in this BSF where data might be read in the
> absence of data, namely if one of the frames in a superframe have size
> of zero (its attempted to read its profile; no actual read takes place
> due to the checks of the get_bits API, but it is nevertheless invalid
> data). See
> https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200530160541.29517-7-andreas.rheinhardt@gmail.com/;
> also see
> https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200530160541.29517-11-andreas.rheinhardt@gmail.com/
> and
> https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200530160541.29517-1-andreas.rheinhardt@gmail.com/

Why did you not apply your bugfixes ?
I think you should apply them

thx

[...]

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Re: [FFmpeg-devel] [PATCH] avcodec/vp9_superframe_split_bsf: Check in size

[Michael Niedermayer]

[-- Attachment #1.1: Type: text/plain, Size: 2656 bytes --]

On Sat, Mar 19, 2022 at 06:38:08PM +0100, Michael Niedermayer wrote:
> On Fri, Mar 18, 2022 at 06:56:19PM +0100, Andreas Rheinhardt wrote:
> > Michael Niedermayer:
> > > Fixes: Out of array read
> > > Fixes: 45137/clusterfuzz-testcase-minimized-ffmpeg_BSF_VP9_SUPERFRAME_SPLIT_fuzzer-4984270639202304
> > > 
> > > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > > ---
> > >  libavcodec/vp9_superframe_split_bsf.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/libavcodec/vp9_superframe_split_bsf.c b/libavcodec/vp9_superframe_split_bsf.c
> > > index ed0444561a..481484a4f0 100644
> > > --- a/libavcodec/vp9_superframe_split_bsf.c
> > > +++ b/libavcodec/vp9_superframe_split_bsf.c
> > > @@ -51,7 +51,7 @@ static int vp9_superframe_split_filter(AVBSFContext *ctx, AVPacket *out)
> > >              return ret;
> > >          in = s->buffer_pkt;
> > >  
> > > -        marker = in->data[in->size - 1];
> > > +        marker = in->size ? in->data[in->size - 1] : 0;
> > >          if ((marker & 0xe0) == 0xc0) {
> > >              int length_size = 1 + ((marker >> 3) & 0x3);
> > >              int   nb_frames = 1 + (marker & 0x7);
> > 
> > There is a second place in this BSF where data might be read in the
> > absence of data, namely if one of the frames in a superframe have size
> > of zero (its attempted to read its profile; no actual read takes place
> > due to the checks of the get_bits API, but it is nevertheless invalid
> > data). See
> > https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200530160541.29517-7-andreas.rheinhardt@gmail.com/;

The get bits API checks for NULL data, if data is not NULL it must be padded
even when size is 0.
Nothing against the 2nd check, but thats a seperate issue


> > also see
> > https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200530160541.29517-11-andreas.rheinhardt@gmail.com/

please apply your bugfixes! especially if its about out or array accesses


> > and
> > https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200530160541.29517-1-andreas.rheinhardt@gmail.com/

thats now found by the fuzzer too, in 45722
if you dont apply your fix i will post a fix

thx

[...]

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Re: [FFmpeg-devel] [PATCH] avcodec/vp9_superframe_split_bsf: Check in size

[Andreas Rheinhardt]

Michael Niedermayer:
> On Sat, Mar 19, 2022 at 06:38:08PM +0100, Michael Niedermayer wrote:
>> On Fri, Mar 18, 2022 at 06:56:19PM +0100, Andreas Rheinhardt wrote:
>>> Michael Niedermayer:
>>>> Fixes: Out of array read
>>>> Fixes: 45137/clusterfuzz-testcase-minimized-ffmpeg_BSF_VP9_SUPERFRAME_SPLIT_fuzzer-4984270639202304
>>>>
>>>> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
>>>> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
>>>> ---
>>>>  libavcodec/vp9_superframe_split_bsf.c | 2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/libavcodec/vp9_superframe_split_bsf.c b/libavcodec/vp9_superframe_split_bsf.c
>>>> index ed0444561a..481484a4f0 100644
>>>> --- a/libavcodec/vp9_superframe_split_bsf.c
>>>> +++ b/libavcodec/vp9_superframe_split_bsf.c
>>>> @@ -51,7 +51,7 @@ static int vp9_superframe_split_filter(AVBSFContext *ctx, AVPacket *out)
>>>>              return ret;
>>>>          in = s->buffer_pkt;
>>>>  
>>>> -        marker = in->data[in->size - 1];
>>>> +        marker = in->size ? in->data[in->size - 1] : 0;
>>>>          if ((marker & 0xe0) == 0xc0) {
>>>>              int length_size = 1 + ((marker >> 3) & 0x3);
>>>>              int   nb_frames = 1 + (marker & 0x7);
>>>
>>> There is a second place in this BSF where data might be read in the
>>> absence of data, namely if one of the frames in a superframe have size
>>> of zero (its attempted to read its profile; no actual read takes place
>>> due to the checks of the get_bits API, but it is nevertheless invalid
>>> data). See
>>> https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200530160541.29517-7-andreas.rheinhardt@gmail.com/;
> 
> The get bits API checks for NULL data, if data is not NULL it must be padded
> even when size is 0.
> Nothing against the 2nd check, but thats a seperate issue

I know that there is no invalid read (and said as much)

> 
> 
>>> also see
>>> https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200530160541.29517-11-andreas.rheinhardt@gmail.com/
> 
> please apply your bugfixes! especially if its about out or array accesses
> 

Will do.

> 
>>> and
>>> https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200530160541.29517-1-andreas.rheinhardt@gmail.com/
> 
> thats now found by the fuzzer too, in 45722
> if you dont apply your fix i will post a fix
> 
> thx
> 
> [...]
> 
> 
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Re: [FFmpeg-devel] [PATCH] avcodec/vp9_superframe_split_bsf: Check in size

[Michael Niedermayer]

[-- Attachment #1.1: Type: text/plain, Size: 2595 bytes --]

On Mon, Mar 21, 2022 at 09:59:00PM +0100, Andreas Rheinhardt wrote:
> Michael Niedermayer:
> > On Sat, Mar 19, 2022 at 06:38:08PM +0100, Michael Niedermayer wrote:
> >> On Fri, Mar 18, 2022 at 06:56:19PM +0100, Andreas Rheinhardt wrote:
> >>> Michael Niedermayer:
> >>>> Fixes: Out of array read
> >>>> Fixes: 45137/clusterfuzz-testcase-minimized-ffmpeg_BSF_VP9_SUPERFRAME_SPLIT_fuzzer-4984270639202304
> >>>>
> >>>> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> >>>> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> >>>> ---
> >>>>  libavcodec/vp9_superframe_split_bsf.c | 2 +-
> >>>>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/libavcodec/vp9_superframe_split_bsf.c b/libavcodec/vp9_superframe_split_bsf.c
> >>>> index ed0444561a..481484a4f0 100644
> >>>> --- a/libavcodec/vp9_superframe_split_bsf.c
> >>>> +++ b/libavcodec/vp9_superframe_split_bsf.c
> >>>> @@ -51,7 +51,7 @@ static int vp9_superframe_split_filter(AVBSFContext *ctx, AVPacket *out)
> >>>>              return ret;
> >>>>          in = s->buffer_pkt;
> >>>>  
> >>>> -        marker = in->data[in->size - 1];
> >>>> +        marker = in->size ? in->data[in->size - 1] : 0;
> >>>>          if ((marker & 0xe0) == 0xc0) {
> >>>>              int length_size = 1 + ((marker >> 3) & 0x3);
> >>>>              int   nb_frames = 1 + (marker & 0x7);
> >>>
> >>> There is a second place in this BSF where data might be read in the
> >>> absence of data, namely if one of the frames in a superframe have size
> >>> of zero (its attempted to read its profile; no actual read takes place
> >>> due to the checks of the get_bits API, but it is nevertheless invalid
> >>> data). See
> >>> https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200530160541.29517-7-andreas.rheinhardt@gmail.com/;
> > 
> > The get bits API checks for NULL data, if data is not NULL it must be padded
> > even when size is 0.
> > Nothing against the 2nd check, but thats a seperate issue
> 
> I know that there is no invalid read (and said as much)

I read what you wrote to quick, i missed this


> 
> > 
> > 
> >>> also see
> >>> https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200530160541.29517-11-andreas.rheinhardt@gmail.com/
> > 
> > please apply your bugfixes! especially if its about out or array accesses
> > 
> 
> Will do.

thx

[...]
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